1. Field of the Invention
The present invention relates to a linear motion and rotation detector that detects a rotational position and a linear motion position of a driven object.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2010-60478 discloses a linear motion and rotation drive apparatus including a motor that linearly moves or rotates an output shaft and a linear motion and rotation detector that detects a linear motion position and a rotational position of the output shaft. In Japanese Patent Laid-Open No. 2010-60478, the linear motion and rotation detector includes a cylindrical linear motion scale that includes linear motion scales provided at regular intervals in a linear motion direction and includes a disc-shaped permanent magnet (rotational) scale) magnetized with two poles in a circumferential direction. The linear motion scale and the permanent magnet are fixed coaxially with the output shaft. Furthermore, the linear motion scale and the permanent magnet are fixed at different positions of the output shaft in an axial direction. The linear motion and rotation detector includes a linear motion displacement detector that detects displacement in a linear motion direction by reading the linear motion scale and a rotation displacement detector that detects displacement in a rotational direction from a magnetic field of the permanent magnet.
A linear motion scale usually has a length corresponding to a linear motion distance of a driven object (output shaft).
Therefore, as disclosed in Japanese Patent Laid-Open No. 2010-60478, when the linear motion scale and the rotational scale are disposed at different positions in the axial direction, a size of the linear motion and rotation detector in the axial direction is increased by at least a length of the rotational scale in the axial direction with respect to the linear motion distance of the driven object.